Effect of microcapsules doping on dielectric performance of self-healing epoxy resin composites

Small physical voids will reduce the dielectric strength of epoxy resin and seriously threaten electronic devices’ reliability. Self-healing is a practical approach to maintain the electrical and mechanical characteristics of epoxy resin. In this research, epoxy resins incorporated with various concentrations of microcapsules were prepared. The microcapsules were treated using a silane coupling agent (KH550) to enhance dispersion. Moreover, the self-healing performance of the epoxy resin incorporated with microcapsules was analysed by FTIR, SEM, AC breakdown strength, tensile strength, dielectric properties and thermal-stimulated current (TSC). The SEM results indicate that the microcapsules/epoxy resin composite has improved self-healing performance compared to pure epoxy resin. DC volume and surface resistivity of epoxy resins altered obviously after incorporation of microcapsules. Furthermore, the AC breakdown strength of epoxy resin doped with 5 wt% microcapsules was found relatively higher than that of pure epoxy resin. The tensile strength of the epoxy with 5 wt% microcapsules increased initially and then decreased gradually with increasing microcapsule content up to 15 wt%. The dielectric constant and dielectric loss of the epoxy resin/microcapsules composites are slightly higher than that of the pure epoxy resin when the content of the microcapsule is 5%, however, with the increase in microcapsule concentration, the dielectric constant and dielectric loss increase due to the weak interaction zone between microcapsules and epoxy resin. The distribution of trap energy and trap density obtained by TSC measurements revealed that 5 wt% have deeper traps and the highest trap energy levels.